A Vaccine for FIV?
The Verdict is Still Out, but Scientists May be Closer to a Breakthrough
By Steve Dale
The United States Food and Drug Administration approved the first ever vaccine for an immunodeficiency virus on March 18th of this year. The vaccine will protect against the feline immunodeficiency virus (FIV), or what is commonly referred to as ‘kitty AIDS’. Because FIV can be fatal, this vaccine will most likely save many lives. Even more compelling are the implications for human medicine.
This vaccine for cats should be available by late summer, according to the pharmaceutical manufacturer, Fort Dodge Animal Health, in Overland Park, Kansas.
“This breakthrough is huge; a vaccine to protect against AIDS is very exciting,” says Dr. Drew Weigner, who is the president of the Academy of Feline Medicine. Weigner, a veterinarian practicing feline-specific care in Atlanta, Georgia, adds that despite his overall enthusiasm – he will not recommend the vaccine – at least not yet.
Here’s the problem with the vaccine: Currently, if a cat is adopted from a shelter, or is exhibiting symptoms of the disease, an anti-body test accurately determines if a cat has FIV. Once a cat is vaccinated with the new vaccine, the anti-body test is very likely to show a positive irregardless if the cat is really sick or not.
The vaccine’s co-creator is Dr. Janet Yamamoto, professor of pathobiology at the University of Florida’s College of Veterinary Medicine in Gainesville. She says the vaccine will be at least 60 percent effective (meaning 60 percent of vaccinated cats will be fully protected). Dr. Arne Zislin, managing consultant of professional services for Fort Dodge Animal Health, says he believes the efficacy will be even higher. But he concedes the vaccine will not be 100 percent effective.
When the new vaccine becomes available it may protect 60 percent – or hopefully even 70 percent or more of indoor/outdoor cats, but it can’t safeguard them all. For example, if your indoor/outdoor cat is vaccinated for FIV and begins acting lethargic, you bring him or her to the vet. With the current testing methods, almost all FIV-vaccinated cats will show positive for the disease, so your cat may appear to have FIV.
Zislin argues that despite problems with diagnosis this new vaccine can and will save lives. “FIV is not curable,” he says. “Veterinary medicine is about disease prevention. If a vaccinated sick cat is exhibiting symptoms which may be indicative of FIV, there are other ways to make a diagnosis. If this new vaccine is not used, cats will continue dying of FIV, which doesn’t make a lot of sense to me.”
The American Association of Feline Practioneers agrees with Weigner’s reluctance to use the vaccine at this time. Dr. Diane Eigner, who is based in Philadelphia, is the association’s president. She says, “We’re happy about the idea of a vaccine for FIV, but we will only recommend such a vaccine if we can accurately test cats for FIV.”
Yamamoto, and Niels (cq) Pedersen at the University of California, Davis worked for 14 years on the development and testing of this new vaccine. She says she anticipated concerns from vets about diagnosing FIV in vaccinated cats. She has an answer, in the form of a plasma test called the RTPCR, which should be made readily available to veterinarians before the end of the year. This test will accurately determine if a cat has FIV, even if the cat has already been vaccinated.
Eigner had not heard about the RTPCR test becoming available, but liked the idea. “If the vaccine doesn’t interfere with diagnosing, we’re all for it,” she reiterates. But like most veterinarians, she added, “I need to learn more about it.”
Dr. Colleen Currigan, a Chicago veterinarian whose practice is limited to cats, is cautiously optimistic. Referring to the RTPCR test, she says she has concerns about the cost and notes that some consumers already feel over-strapped with veterinary costs.
Another issue is the make-up of the new FIV vaccine itself, which is referred to as a killed vaccine. Cancer associated with the vaccine site is deadly, and it seems the adjuvant or additional substance which makes killed vaccine effective might possibly be linked to these cancers. But no one knows for sure.
In fact, no one knows for sure how often vaccine-associated cancer even occurs. In 1996, the Vaccine-Associated Feline Sarcoma Task Force estimated that one to four of every 10,000 cats may be diagnosed with vaccine-associated sarcoma. However, Dr. Richard Ford, professor of medicine at the College of Veterinary Medicine at North Carolina State University in Raleigh, indicates that vaccine-associated sarcoma may actually occur even more often – depending on the specific vaccine.
In her research, Yamamoto says there wasn’t a single adverse reaction in tests to the new FIV vaccine – let alone a report of cancer. Zislin is confident the vaccine will be safe. The adjuvant used by Fort Dodge is proprietary information, but it won’t be the same adjuvant type used in the feline leukemia vaccine and rabies vaccine where problems associated with cancer have been reported.
Eigner adds, “As veterinarians administering vaccines, we weigh risks and benefits daily.” In other words, what’s the risk of giving the vaccine compared to the benefit of the vaccine? “The most important thing is that every single cat is evaluated as an individual, and that’s true for all vaccines,” she says.
Yamamoto says human researchers have been working with her, as their process of developing a vaccine for human AIDS continues. In fact, a great deal of the funding for Yamamoto’s work came from the National Institutes of Health with just that thought in mind. She says, “I no longer believe it’s a matter of if there will be a vaccine for human AIDS, but instead when such a vaccine will become available. Human AIDS and FIV are very closely related.”
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